[sitecore-jss-react] Allow defer prop on VisitorIdentification component

[pzi]

Add support for the defer prop to the VisitorIdentification component to support non-blocking script loading.

This attribute allows the elimination of parser-blocking JavaScript where the browser would have to load and evaluate scripts before continuing to parse. async has a similar effect in this case.

Description / Motivation

Opt-in to make VisitorIdentification non-blocking.

Testing Details

Component does not have any tests.
Setting defer to true will render <script defer ...></script>.
Setting defer to false or undefined will render <script ...></script>.

Making the prop optional makes this a non-breaking change.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[pzi]

@ambrauer @sc-addypathania some feedback on this would be appreciated :)

[ambrauer]

Looks good to me, thanks for the contribution!

FYI @Sitecore/jss-dev-reviewers I've added a corresponding task to our backlog to cover any additional testing scenarios I might be missing (e.g. probably time we add unit tests for the component 😊).

[pzi]

Thanks @ambrauer 🙏🏼